Improved Kaiser-Bessel Window Parameter Selection for Gridding

Introduction The gridding algorithm is frequently used to reconstruct an image from a non-uniformly sampled k-space. An important part of the algorithm is a convolution with a window. Usually, the Kaiser-Bessel window is used [1], which has a width L and a parameter B. A criterion for selecting an optimal value for B is the relative amount of aliased energy (including roll-off correction) of the window as used by Jackson [2]. In this abstract we show that the values for B found in [2] are not always optimal and introduce a method to find improved values for B given the sampling distribution. Method Resampling the convolved samples to a Cartesian grid in k- space causes aliasing. We write the aliased energy as: Z jxj?FOV fi fi fi fi c(x) \Delt

Accelerated Bayesian MR Image Reconstruction

This paper concerns reconstruction of 2D and 3D MR images from raw, sparsely and nonuniformly sampled k-space signals. In particular, it pertains to iterative Bayesian image reconstruction and acceleration of the attendant convergence to the `Maximum A Posteriori' (MAP) image. Significant acceleration is achieved by weighting of the Likelihood term with the inverse of the sampling density. In addition, weighting can reduce the sensitivity to measurement errors in samples that have been assigned a low weight. We present applications to 2D sparse spiral scanning and 3D random scanning

A dual sensor spin trap for use with EPR spectroscopy

Redox active metal ions, carbon-centered radicals, and oxygen-centered radicals are important to oxidative stress. A radical detector combining a nitrone spin trap, a phenol, and a cyclopropane radical clocklike unit was prepared and used with EPR spectroscopy to detect and distinguish between hydroxyl radicals, methyl radicals, and iron(III) ions. Iron(III) reacts with the phenol unit inducing opening of the cyclopropane ring and cyclization to generate a stable nitroxyl radical

The colour and stereo surface imaging system (CaSSIS) for the ExoMars Trace Gas Orbiter

The Colour and Stereo Surface Imaging System (CaSSIS) is the main imaging system onboard the European Space Agency’s ExoMars Trace Gas Orbiter (TGO) which was launched on 14 March 2016. CaSSIS is intended to acquire moderately high resolution (4.6 m/pixel) targeted images of Mars at a rate of 10–20 images per day from a roughly circular orbit 400 km above the surface. Each image can be acquired in up to four colours and stereo capability is foreseen by the use of a novel rotation mechanism. A typical product from one image acquisition will be a 9.5 km×∼45 km swath in full colour and stereo in one over-flight of the target thereby reducing atmospheric influences inherent in stereo and colour products from previous high resolution imagers. This paper describes the instrument including several novel technical solutions required to achieve the scientific requirements